Anatomy and Physiology: Chapter 18- Urinary-System.pptx

Anatomy & Physiology

1. Chapter 18 Urinary System and Fluid Balance Lecture Outline Seeley’s ESSENTIALS OF ANATOMY & PHYSIOLOGY Eleventh Edition Cinnamon VanPutte Jennifer Regan Andrew Russo Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC.

2. Urinary System The urinary system is the major excretory system of the body. Some organs in other systems also eliminate wastes, but they are not able to compensate in the case of kidney failure.

3. Urinary System Functions Excretion Regulation of blood volume and pressure Regulation of blood solute concentration Regulation of extracellular fluid pH Regulation of red blood cell synthesis Regulation of Vitamin D synthesis

4. Kidney Structures Renal capsule: connective tissue around each kidney protects and acts as a barrier Hilum: indentation contains renal artery, veins, nerves, ureter

5. Kidney Structures Renal sinus: contains renal pelvis, blood vessels, fat Renal cortex: outer portion Renal medulla: inner portion

6. Kidney Structures Renal pyramid: Cone shaped structures in the medulla whose bases project into the cortex Renal papillae: tip of pyramids which drain into calyces Renal pelvis: where calyces join together narrows to form ureter

7. Ureters and Urinary Bladder Ureters: small tubes that carry urine from renal pelvis of kidney to bladder Urinary bladder: in pelvic cavity stores urine can hold a few ml to a maximum of 1000 milliliters

8. Urethra Urethra: tube that exits bladder carries urine from urinary bladder to outside of body I nternal urethral sphincter smooth muscle surrounds urethra at the junction of the urinary bladder and prevents urine from leaving the bladder

9. Urethra External urethral sphincter: formed of skeletal muscle surrounding the urethra near the pelvic floor. allows a person to voluntarily start or stop the flow of urine out of the urethra

10. Nephron The nephron is the functional unit of the kidney. Each kidney has over one million nephrons. The nephron includes the renal corpuscle, proximal convoluted tubule, loop of Henle, distal convoluted tubule and collecting duct

11. Renal Corpuscle The filtration portion of the nephron Glomerulus: A network of capillaries twisted around each other like a ball of yarn Bowman’s capsule: enlarged end of nephron surrounds glomerulus opens into proximal convoluted tubule contains podocytes (specialized cells around glomerular capillaries)

12. Renal Corpuscle Bowman capsule consists of two layers: Outer layer - simple squamous epithelial cells that become cube-shaped at the beginning of the proximal convoluted tubule Inner layer - cells called podocytes, which wrap around the glomerular capillaries

13. Proximal convoluted tubule: where filtrate passes first drains filtrate from Bowman capsule Loop of Henle: contains descending and ascending loops water and solutes pass through thin walls by diffusion Nephron Components

14. Nephron Components Distal convoluted tubule: structure between Loop of Henle and collecting duct Collecting duct: empties into calyces carry fluid from cortex through medulla

15. Types of Nephrons Juxtamedullary nephrons renal corpuscles are deep in the cortex near the medulla long loops of Henle extend deep into the medulla Well adapted for water conservation About 15% of nephrons

16. Types of Nephrons 2. Cortical nephrons Renal corpuscles distributed throughout the cortex (outer portion) Loops of Henle are shorter and closer to the outer edge of the cortex than juxtamedullary nephrons

17. Characteristics of Renal Corpuscle 1. Porous capillaries - highly permeable due to the presence of pores. Neither large proteins nor blood cells can fit through them. 2. Porous inner layer of Bowman capsule - A basement membrane lies between the endothelial cells of the glomerular capillaries and the podocytes of the Bowman capsule.

18. Characteristics of Renal Corpuscle 3. High pressure An afferent arteriole supplies blood to the glomerulus for filtration. An efferent arteriole transports the filtered blood away from the glomerulus. Efferent arteriole has smaller diameter than afferent arteriole creating a high pressure in the capillaries.

19. Filtration Membrane The structures in the corpuscle make up the filtration membrane. Consists of capillary endothelium, the basement membrane, and the podocytes of the Bowman capsule Filtrate is the fluid filtered from the glomerular capillaries. E nters the lumen (cavity) inside the Bowman capsule.

20. Flow of Filtrate through Nephron Renal corpuscle Proximal convoluted tubule Descending loop of Henle Ascending loop of Henle Distal convoluted tubule Collecting duct Papillary duct

21. Urine Formation 1. Filtration – occurs in the renal corpuscle, blood plasma leave glomerulus and enters Bowman space 2. Tubular Reabsorption – involves removing substances from the filtrate and placing them back into the blood 3. Secretion – involves taking substances from the blood at a nephron area other than the renal corpuscle and putting back into the nephron tubule

22. Urine Formation-Filtration Movement of water, ions, small molecules through filtration membrane into Bowman’s capsule 19% of plasma becomes filtrate 180 liters of filtrate are produced by the nephrons each day 1% of filtrate (1.8 liters) become urine, the rest is reabsorbed

23. Urine Production-Reabsorption 99% of filtrate is reabsorbed and reenters circulation The proximal convoluted tubule is the primary site for reabsorption of solutes and water The descending Loop of Henle concentrates filtrate Reabsorption of water and solutes from distal convoluted tubule and collecting duct is controlled by hormones

24. Urine Production—Secretion Ammonia secretion is passive. Secretion of H + , K + , creatinine, histamine, and penicillin is by active transport. These substances are actively transported into the nephron. The secretion of H + plays an important role in regulating the body fluid pH.

25. Regulation of Urine Concentration and Volume Renin-angiotensin-aldosterone - regulates blood pressure; controls fluid & electrolyte balance Antidiuretic hormone (ADH) - helps blood vessels constrict; controls amount of water & salts in the body Atrial natriuretic hormone - acts on kidney to decrease sodium reabsorption

26. Urine Movement Micturition reflex: activated by stretch of urinary bladder wall action potentials are conducted from bladder to spinal cord through pelvic nerves parasympathetic action potentials cause bladder to contract stretching of bladder stimulates sensory neurons to inform brain person needs to urinate